The overall object of the proposed research is to assure a continuing year round supply of fertile purple sea urchins (Strongylocentrotus purpuratus) as a research resource. The approach to this study is at two levels. Primarily, there will be a close examination of the fertility of sea urchins derived from a special deep water site as a function of season. In general it is known that sea urchins are fertile for several months during the year, and we intend to extend this knowledge to a more precise and detailed level for the chosen locality, the Pt. Loma kelp bed near San Diego, Calif. For example, the effect of microhabitat, temperature, and food availability will be examined in relation to fertility and the ability of gametes to undergo normal development. Preliminary information indicates that there are particular microhabitat parameters which can extend the fertile season of populations of this species to the whole year. Coupled with investigations of sea urchin fertility in the animal's natural habitat, we intend to investigate systems for the laboratory culture and maintenance of sea urchins. Preliminary information indicates that sea urchins can be maintained in the laboratory for extended periods at high levels of fertility. We will examine critically those parameters in the laboratory environment which will enhance the laboratory maintenance of sea urchins in a fertile state. We will examine the effects of such parameters as temperature, urchin density, and diet. We also intend to examine conditions which will enable spawned urchins to undergo accelerated gametogenesis under laboratory conditions. At the same time we will further develop the capacities of the chilled running sea water culture system now in use.